magnum 21 trimaran review

Design Reviews & Comparisons

With the amount of work required to undertake articles comparing various existing boats, it has been decided to deal with this challenging subject through a number of separate reports that will be available at the lowest possible cost. The first of these has now been on sale for several years (at just $7), and presents some personal thoughts and assessment by the writer (plus numerous photos) about the following designs:

In addition to the above, this Report#1 also includes two spreadsheets, giving a wealth of technical data for each design, as well as the results of formulae for comparisons dealing with cost, build time and performance. This data is not only given for the 12 small tris noted above, but for a total of 20 small tris that include the following:

Magnum 21; Magnum 21S; Kolibri 23; Cardiff 21, A21 and Z65; Warren 23 Mk2; Scarab 670; Scarab 22; Corsair Sprint; Discovery 20; Leneman L7; Day Tri20; Spitfire 20; KH-23; KH-24; Trinado; Tremolino Mk4; Farrier K24T and F22.

After completion, the report was sent out to five internationally-noted designers, and their appreciated comments on this work are noted at the base of the text on this page Small Trimarans Review

So if this interests you as I think it will, please go to the Sales Page to place your order. It's quick and it's safe. The report will then be delivered to you as a PDF file for printing out at home in full color. We recommend to select the 'Print Both Sides' print option that comes with most printers today and then get the 22 pages plus a cover, wire bound for future use and reference.

Footnote: As stated in the Report, the reviewing comments and comparison data are naturally only that of the writer, but they do come from 60+ years of experience with small boats, the personal ownership of 4 small trimarans over the last 30 years, as well as qualifications as a professional engineer and naval architect from one of the most reputable universities in the world in this field.

On receipt, please let us know if you've enjoyed this report and have any suggestions for another. Many have in fact written in already with most favorable comments. Thank you.

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Yachting Monthly

• Digital edition

Astus 20.5: Fast, fun and affordable trailable trimaran

• David Harding
• August 20, 2021

For fast yet undemanding sailing, easy trailing and simple camper-cruising, the Astus 20.5 trimaran is likely to find wide appeal says David Harding

The Astus 20.5 is taut and responsive to sail. Credit: David Harding

Product Overview

• Fast and easy to sail
• Can be trailed behind a small car
• Easy to reduce beam for marina berthing
• Less accommodation than a monohull of similar size
• Rigging process could be simplified
• Slightly stark interior finish

Manufacturer:

Price as reviewed:.

Boats that are small and light enough to keep in your driveway and trail to where you want to sail make a lot of sense.

One drawback, however, is that they tend to be slower than bigger boats – especially if they’re of a size and weight that allows them to be easily managed short-hand, both afloat and ashore.

If you want to sail from Poole to Weymouth for the weekend in a 20ft trailer-sailer, for example, it might take a while.

This is where speedy trailable trimarans like the Astus 20.5 come in.

When I sailed its predecessor, the 20.2, about 10 years ago, we regularly hit 15 knots on a reach without breaking sweat and maintained an easy 6.5 knots upwind.

This 20 footer can match 50 footers for speed. Credit: David Harding

You can cover a lot of ground at those sorts of speeds.

I first met the Astus 20.5 at the Düsseldorf Boat Show in 2019. Since it’s a newer boat and designed by no less a design team than VPLP, I had high hopes that it would offer even more than the 20.2.

Quite apart from the sailing potential, the trailing is as simple as can be with a boat like this.

If you choose the resin-infused hull, the Astus 20.5 weighs under 500kg (1,100lb), or just over 500kg with the standard solid laminate.

The lighter weight means you can use an unbraked trailer , saving money, maintenance and yet more weight, so you can trail it behind a normal hatchback vehicle.

Getting somewhere fast under sail is one thing. Having somewhere to sleep when you arrive is another.

The Astus 20.5 is simple to sail for two people. Credit: David Harding

Though its cabin is smaller than on a monohull of similar size, the Astus provides seating, stowage and space for a companionable couple to be able to stretch out.

Then of course you have the trampolines each side on which you can rig a tent for more sleeping space.

The opportunity for a sail on the Astus 20.5 finally came when Hein Kuiper of Boats On Wheels brought his first demonstrator to the UK.

In fact we went out twice – first for a photo session in Poole on a brisk winter’s day and then a few months later in Chichester Harbour.

Since the boat arrived in Poole on its trailer, I was able to see how it went together.

Pulling out the hulls is pretty straightforward: their aluminium beams slide in and out of the fixed beams on the main hull. You can do that ashore or afloat.

There’s nothing complicated about raising the rig, either, and it can all be done singlehanded .

The whole process, from arriving with the trailer to sliding the boat into the water, took Hein a couple of hours or so the first time or two (comparable with a monohull of similar size, he reckons) but would undoubtedly get quicker with practice.

Continues below…

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Dragonfly 28 Sport

Whether you choose the standard or the Sport version, the mast is the same height.

The difference is that the latter comes with a square-top mainsail to give appreciably more sail area.

If you want to save as much weight as possible and make raising and lowering the mast easier, you can have it in carbon. A wing mast is another option.

The rig and hardware don’t appear to be modified in any way as a concession to the boat’s trailer-sailer nature.

Here and there, the odd ready-made loop or strop would save fiddling around with bits of line.

It is basic down below but there’s seating and sleeping space for two people. Credit: David Harding

All that is forgotten as soon as you’re under way.

On our second outing, once the electric outboard had pushed us out of Northney Marina – where the boat proved to be surprisingly manoeuvrable with the centreplate fully down – we headed off on a beam reach at 12.5 knots in 12-15 knots of wind.

In most boats, 12.5 knots would be going some. In this 20-footer, it felt perfectly relaxed.

Over the course of the following couple of hours we covered every point of sail including, of course, reaching under spinnaker.

With the gusts rarely exceeding 16 knots in the flat water of the harbour, we didn’t quite manage to break 15 knots.

It wasn’t a bad speed-to-effort ratio nonetheless.

The boat felt rock solid the whole time, and I knew from the photo session in Poole that she could carry the kite on a beam reach in appreciably more wind than we had in Chichester.

It is easy to reduce the beam of the Astus 20.5 for marina berthing. Credit: David Harding

It’s hard to imagine that 20 knots wouldn’t be perfectly achievable.

Upwind we maintained between 7 and 8.5 knots most of the time.

As you would expect, you need to keep the bow down a little to maintain full power.

You also need the purchase of the 6:1 mainsheet to maintain sufficient tension in the upper leech. It makes a big difference.

You won’t need more than two people to go out and have fun on the Astus 20.5. Credit: David Harding

Tacking was pretty positive provided we had adequate boatspeed going into the tack, and leeway appeared minimal.

All told the Astus 20.5 was great fun to sail and easy to manage two-handed.

There was little for a third person to do except enjoy the ride or contribute to the righting moment by joining the helmsman on the windward trampoline.

If you were racing, you could use a longer tiller extension and fit toe-straps to maximise the advantage.

Beating our way back up the harbour, we demonstrated the windward ability of the Astus 20.5 by sailing straight past a 15m (49ft) monohull.

Creature comforts aboard the Astus 20.5

David Harding has been testing boats for decades and is also a sailing photographer

Above decks the Astus offers a vast amount of sitting and lounging space thanks to the trampolines.

Down below, the hull’s narrow beam makes things cosy but you still find a seat either side, space for a chemical toilet under the aft end of the berth and a fair amount of stowage beneath and to either side of the companionway.

The centreboard is offset to port to leave the middle of the boat clear.

The finish is simple and uncomplicated, largely to save weight. There would be plenty of scope to fit a slide-out galley and devise lightweight stowage solutions to make better use of the space.

Astus 20.5: the test verdict 

More than anything else, this boat is tremendous fun.

She feels taut and responsive to sail. I found that it took an hour or so to begin to find her sweet spots, but after that she just makes you want to sail her.

She inspires confidence and is easy to handle, too. In most conditions you could manage perfectly well single-handed and for cruising you won’t need more than two.

The Astus 20.5 has less accommodation than a monohull of similar size

Then there’s the speed. No matter whether or not you’re in a hurry to get anywhere, it’s easier to slow down in a fast boat than to speed up in a slow one.

Speed is fun in itself, and it’s hard not to enjoy sailing straight past a monohull more than twice your length.

Niggles are relatively few.

I thought the rudder blade could do with a touch more balance and I wasn’t sure that the fixed end of the 2:1 jib sheet was quite far enough aft on deck.

Other than that, it all works.

Hardware is mostly from Harken and the spars are by Sélden, so there’s no skimping in these departments.

Would she suit you and your crew?

The Astus 20.5 will attract attention. Several people stopped for a chat and to admire her back in Northney having seen her on the water.

If you’re a dinghy sailor moving up but not ready to slow down, this is a good choice.

Just as much interest is coming from big-boat sailors moving down or wanting a second, smaller boat that still has a good cruising range. Few boats of this size go so fast with so little effort.

The Astus 20.5 is ideal for exploring harbours, estuaries and rivers

As for the inevitable monohull-versus-multihull debate, there are trailable, family-friendly boats of this size with one hull that sail very nicely.

I have clocked over 12 knots in one or two, but only under spinnaker, with good sailors on board and not for sustained periods.

As long as you’re prepared to accept that sailing regularly at double-figure speeds means sacrificing some interior volume, the Astus could suit you perfectly. And for exploring harbours and estuaries, camper-cruising and nudging into the beach, it’s absolutely ideal.

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magnum 21 ... maybe

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I am helping my Grandsons renew an older Trimaran. We do not know the builder for certain. I think that it may be an older Magnum 21. I say older because looking at the newer ones, it does not have the open transom, instead it is a closed flat stern, It is 21 ft. long. It has folding pontoons. They lift up on hinged arms. Can anyone help me ID the boat. Also the old beatup sail has the Vecter logo on it. I am looking for a replacement rudder. tiller and sails. The main luff is 21' 3.5", foot is 8'7" it has a 33 " roach. Any help would be great!  

it would help if you posted photos of the boat. the easiest way to post photos is to upload them to a photo sharing site like flickr.com and link to the images using the yellow postcard like image link icon in the toolbar.  

BTW, it sounds like it might be a farrier-design, like the tri-trailer or the tramp. You can see many of the older Farrier designs HERE .  

Here is a pictute of the 21 ft. trimaran. Can anyone identify the make/model? The outriggers fold up.  

Attachments

Do you have a better photo... that one pretty much blows chunks... Can't see any detail in the hulll and detail of the crossbeams and hull would help with identifying it. Also can't make out the ama hull lines. A closer viewpoint would also show more of the deck and the shape of the hulls. Is it a centerboard or a daggerboard design??  

I uploaded the better photos to flickr.com. The tags start with "unknown trimaran". Hope you can ID the boat. Thanks!  

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looking for a 21 ft trimaran

Discussion in ' Boat Design ' started by arzpengwen , Sep 11, 2004 .

arzpengwen New Member

Hello, I'm am looking for a recent design of a 20/21ft trimaran... I have only seen the Magnum 21 ( www.virusboats.com ). Is the other trimaran like Magnum 21 ? ( Dragon fly 800 and F24 are too expensive for me) Thanks very much in advance, Bertrand  

Ilan Voyager Senior Member

arzpengwen said: Hello, I'm am looking for a recent design of a 20/21ft trimaran... I have only seen the Magnum 21 ( www.virusboats.com ). Is the other trimaran like Magnum 21 ? ( Dragon fly 800 and F24 are too expensive for me) Thanks very much in advance, Bertrand Click to expand...

Tad Boat Designer

Bertrand, Multihulls World did a comparision test in July/Aug 2004 issue between the Magnum 21 and two other camp cruising multihulls. One is a tri called the Tricat 22, the other a cat, the Drake 18. The Tricat appears to be somewhat more expensive than the Magnum and comes in either a Raid version with keels, or a sport version with daggerboards. see Tricat All the best, Tad  

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Also the Newick desiged Tremolino has just come back into production in France. The builder is Chantier Marijon, see marijon Tad  

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• Boats and Items for sale

Magnum 21 Trimaran For Sale

By NACRAJON , October 23, 2016 in Boats and Items for sale

• Start new topic

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I moved from a Taipan 4.9 to a trimaran as I had a growing family as the Taipan was to flighty for family outings. Some of you may be in a similar situation.

Light and responsive sailing trimaran that is perfect for beach cruising or dinghy type camping. This is a French made trimaran that has over 400 built and is a good club racer/ family dayboat/ coastal raid boat.

EU Category C, unsinkable ( all three hulls are foam filled), able to legally carry 6 adults along the coast or 8 adults in smooth waters.

It has been club raced last two years and is competitive with Farriers and Wetas. Think of it as a modern incarnation of a Haines / OSTAC. But it weighs 350kg not 600kg.

2005 model with later model beams that allow easier assembly. I regulary single hand this and get it from the trailer to the water in an hour by myself.

With pop up tents on the tramps you have a two bedroom cruiser and I have done week long camping trips on the Hawkesbury River. Has also been single-handed around French and Phillip Islands in less than one day.

Has a 3 hp Yamaha that has less than 10 hrs. I find the motor is generally left at home as the boat is so good to sail, the motors not needed. If I need propulsion with no wind the boat is easily paddled.

Improvements from stock by professional marine engineer :

-centerboard reshaped to NACA profile with composite reinforcement

- Centreboard slot gasket replaced

-rudder reshaped to NACA profile

-All running rigging replaced

-Mast crutch for single person raising and lowering

-Furling Jib

- 2nd reef in mainsail

Has high quality full roller breakback French made trailer that is hot dipped gal and used primarily in fresh water.Zero rust.

Can deliver within 500km of Canberra. Utube Magnum 21or view Yachthub for more info.

Jon in Canberra,  ACT

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• 2 weeks later...

Should have given a price, $12,000.

Price drop, $11000. Keen to sell as I have bought a new boat

• 3 weeks later...

Open to offers

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SPECIFICATION

Magnum 21S Trimaran

Country/Region of Manufacture: France

Hull identification number: MO287 D 505

Magnum 21S - 2005 year. Stored in barn in Sussex This boat has had a lot of upgrades / work done to make it easy to sail shorthanded. It is great for daysailing adventures with a real turn of speed. 12 knots is not uncommon... Upwind performance is good in flat water and she points much better than a Hobie cat or Dart. She can be also be pulled up on a beach.

Draft is 1.4m with centreboard down. Bothe the rudder and centerboard have breakaway cleats that pop up if you touch the bottom. This prevents any damage. With foils up she draws a few inches. Can be stored on the trailer, mooring or marina.

With practice, 2 people can rig the boat from trailer to sailing in under an hour. There are some good videos on line that give tips. She can easily be sailed singlehanded, including the Code Zero/furling gennaker. Unsinkable design with foam filled hull and armas. I have had a lot of fun with this boat in UK and Greece but selling as I now have a larger yacht.

• Specification • Repainted topsides (Toplac) and polished white areas. Needs re-waxing /polishing but paint good. • Full bespoke storage cover - covers main hull and trampolines with zip cut outs for mast and shrouds. Made from Sunbrella - high quality with zips etc. • New composite rudder (2016 from Virus) with spare wooden original (in VGC) • Reinforced trampolines in good condition plus a brand new spare set from Virus.

One of the trampoline rods is missing a plastic end cap - replaced with gaffer tape. • New halyards, trapeze lines and some new sheets (2016). • Upgraded kicker with clam cleat 2016. • New jib - made by Batt sails 2016 • Spare jib in decent condition • Mainsail with 2 reefing points. One small repair but sail in good condition • Fully battened Mainsail converted to track cars - much easier to hoist and lower.

• Jib chute with line to raise. Protects jib from UV • New mainsail cover (2016). Much easier to leave main rigged than removing main each outing. • Lazy jacks • Topping lift • Upgraded metal camcleats on mast and boom. Some are side entry for ease of use.

Plastic lam cleats replaced • Barely used asymmetric spinnaker with new Hyde snuffer (2016) • Code zero on continuous line furler. Works very well for short handed or higher winds reaching up to 65 deg apparent. * Extending bowsprit for spinnaker. Plastic bush on bow for Bowsprit is cracked and has repair to limit any water ingress. • Furling gennaker • New main block with ratchet and adjustable sheeting angle (much easier to handle in a blow) • Danforth style anchor with Anchor bag.

• Additional cleat and fairlead for stern mooring or anchoring • Masthead wind vane (installed 2016) • Coppercoat antifouling • Compass• GPS "speed puck" readout mounted at base of mast. • Trailer with new wheel bearings 2016. £500 spent. I am selling without outboard but have a 6hp 4 stroke Mercury outboard in good condition fresh from service that I could negotiate to include for additional price. I also have a 10 HP Honda 4 stroke that gives 10knots under power.

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Discovery 20 Trimaran

See  Discovery 21 .

The Discovery 20 trimaran is a fast, fun daysailer with the potential to be a camper/cruiser for the adventurous. The D 20 design has been updated as an exciting and powerful new daysailer. It is available as a kit or a complete boat. This design is intended for enjoyable day sailing, although there is space below deck for camping gear. There is a 7' by 7' cockpit that is roomy for 4. You sit upright, with a backrest, not sprawled on a trampoline. My 75 year old mother-in-law found the boat very comfortable. The D-20 is quite fast; the all up weight of the boat is 527 pounds. She utilizes a daggerboard, a rotating aluminum mast and streamlined crossbeams. Construction is wood/epoxy/glass composite.

I really never appreciated how fast the Discovey is until about 10 years after she was designed when I raced mine in a Wednesday night yacht club series against a new Newick 24' trimaran (longer, wider, taller rig, new laminate sails). The other boat was sailed by a very experienced sailor and I was expecting to get my butt kicked. During the first upwind leg (in about 8 knots breeze) the Discovery 20 blew everything away, including a fleet of Etchells. I was so impressed I hove to at the weather mark and waited for the other tri to catch up so that I could get a better comparison on the down wind leg (he had a spinnaker I didn't). As expected, I lost some ground here but not really that much, and I was able to get it all back on the next upwind leg.

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